In the context of cavity wall structures or construction, the walls are typically formed of two wythes. These may both be of masonry, the wythes being spaced apart to form a vertical space or cavity therebetween. Alternatively it may have an outer masonry wall such as of bricks, with an inner building wall of wood, wallboard, concrete, tile or similar commonly used interior wythe materials.
In conventional cavity wall construction, flashing is typically installed atop the foundation to direct water out of the bottom of the cavity (for instance), in association with weep holes or other elements which will enable water to escape or migrate through the outer masonry wythe. Water in the cavity is undesirable for many reasons.
Flashing typically used may be in the form of a membrane, such as a rubberized material, as well as sheet metal, just to name two fairly standard types of flashing material. It is known to provide a downturned edge along the part of the flashing which will be on the outside of the outer wythe. This is referred to as a drip edge. It is also known to construct the flashing in a hybrid manner, such that a relatively flexible membrane is used in conjunction with a relatively inflexible drip edge. The flashing may ordinarily be affixed in position using adhesive, for instance.
Building corners most often meet at ninety degree angles. The flashing can be cut to size in order to meet at a ninety degree angle in these instances. Additionally, a drip edge for use in conjunction with the flashing can be provided which is pre-formed in manufacture with parts forming a ninety degree angle. However, builders and architects are not confined to easy ninety degree corners, and corners may become obtuse as well as acute in angulation.